1. Field of the Invention
This invention relates to directional control of fluids at supersonic speeds. Particularly, this invention relates to directional control of gases similar to those flowing within or discharged from a gas laser, wind tunnel, MHD machine, or propulsion device. In even greater particularity, the present invention relates to controlled gas patterns which exhibit well behaved properties due to the nature of the supersonic nozzle which creates the supersonic flow.
2. Description of the Prior Art
Conventional one dimensional supersonic flow devices are constructed to allow gas to flow from a high pressure chamber through a linear array of supersonic nozzles into a low static pressure cavity region with a flow which is essentially parallel at a near constant mach number. Partial pressure recovery of the gases is accomplished by passing the supersonic flow through a converging diverging diffuser or second throat.
While two dimensional cylindrical outwardly flowing supersonic flow devices have been mentioned in the art, no previous experiments on inwardly flowing gas lasers have been reported. All prior art two dimensional devices are outwardly expanding supersonic flow devices. Outward expansion in gas lasers suffers the disadvantage that, as the gas expands geometrically outward, the flow mach number increases over and above that needed for good laser operation, typically mach four or five, which worsens the problem of pressure recovery. The total pressure loss across a normal shock increases with increasing mach number. Thus, the pressure recovery of conventional material diffusers decreases with increasing mach number. An ideal diffuser will theoretically recover the total pressure of the higher mach flow as well as a lower mach flow assuming a normal shock just downstream of the diffuser throat. However, ideal diffusers are not realized in practice.
Outwardly expanding supersonic flow devices also suffer from design limitations due to the requirement that the inlet flow be unchoked. This requirement leads to a flow limitation through the device due to the constraint of subsonic flow on the upstream side of the throat. This requirement severely constrains the design of a practical device for many applications.
An inwardly flowing gas laser retains many of the packaging and weight reduction quantities provided in outwardly expanding flow designs. In addition it offers a great potential advantage in pressure recovery of the flow. The gas, after expanding to the required mach number in the nozzle region, becomes generally and gradually compressed through the geometrical contraction effect. If this contraction is continued, and followed by an expansion, the flow is made to pass from supersonic to subsonic, potentially allowing very efficient pressure recovery.